In general, I try to avoid talking in absolutes, but “why the vast majority of the population need heavy days” just doesn’t quite have the same ring to it.

Firstly, “heavy” is relative… If each athlete lifts a load that is relatively heavy for him or her then they are participating in a heavy day… As long as correct mechanics are instilled / reinforced, heavy days are for everybody, whether young, old, fit, unfit, experienced or inexperienced.

Heavy days build top end strength. This is important not just for short duration, high power efforts, but also for longer duration efforts. Have a look at the power curve below… ​

During a workout, power output decreases with time, meaning that an athlete’s work capacity in very short time domains sets the theoretical limit for the entire curve.

Using the graph above, we can see…

The 98-99% group: - Produce over 1600 watts at the 1 second mark- Produce around 1000 watts at the 30 second mark - Produce around 400 watts at the 20 minute mark

The 40-50% group: - Produce around 1000 watts at the 1 second mark- Produce around 700 watts at the 30 second mark - Produce around 300 watts at the 20 minute mark

Even well after an hour, the 98-99% group is still putting out more power than the 40-50% group.

Essentially the more power you can produce in short duration efforts, the more power you can produce throughout long duration efforts. Obviously experience and specificity needs to be considered in the upper echelons of sport, but in general, if we increase your power via a smart strength and conditioning approach, your running / cycling / swimming / Fran / etc times improve…

The graph below - while I feel it isn’t as scientific as the one above and certainly doesn’t reflect everyone's performances - does an ok job of illustrating this point for CrossFitters.

​By mixing high power, short duration efforts with lower power, long duration efforts we can raise this entire curve upwards.

It is [generally] a big mistake to not have days solely dedicated to increasing your top end strength.

Is it [CrossFit and heavy days] all about power generation?

Yes and no…

Our goal is to increase health markers…

Blood pressure, body fat, bone density, etc - they’re all elements of fitness, and can all be improved with heavy days...

- Strength training has been shown time and again to improve heart function and decrease blood pressure. It improves arterial function and decreases inflammation. As far as blood pressure goes – a review found that across eight trials, systolic blood pressure was reduced by 6.2mmHg – more than double the benefit of typical blood pressure lowering medications. Less inflammation, lower systolic blood pressure and improved arterial function can only mean good things – a reduced risk of cardiovascular disease.

- A study on 28 slightly overweight and untrained men found that a weight lifting program followed three times a week for eight weeks lost 3kg of body fat – a decrease of 13% body fat – and gained 3kg of muscle.

- Former athletes who incorporated heavy weight lifting into their training had much stronger bones as they aged – this meant a 50% lower chance of fracture in men, and a 20% lower risk of fracture for the women.

With solid dietary guidelines and smart strength and conditioning, we can improve your health markers. If we improve your health markers we increase your fitness.

And what is fitness?

You could call it something like "super-wellness", but really a more scientific definition would be how much work you can do in any given time domain… Your power output, basically.

For those interested in the physiological changes brought about by heavy days - reduced body fat, an increase in bone density, greater muscle mass - I wrote about it a while back…

“You may be able to coerce fat cells into becoming just about anything you want. Fat tissue belongs to a class of tissue called connective tissue - this includes blood, bone, muscle, collagen, etc - with the current belief being that a connective tissue cell permanently retains its ability to transform into another cell type whenever it is given the chemical signal to do so. This process - called transdifferentiation - can make fat cells leave your adipose tissue and migrate to become new muscle, bone or even brain cells… You can control this chemical signalling with what you put in your mouth and what you expose your body to…”